Advancement Roger shortly found in Fleet Street (8)
I believe the answer is:
progress
'advancement' is the definition.
(I know that advancement can be written as progress)
'roger shortly found in fleet street' is the wordplay.
'roger shortly' becomes 'rog' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'found in' means one lot of letters goes inside another.
'fleet street' becomes 'press' (Fleet Street can mean the UK newspaper industry).
'rog' going into 'press' is 'PROGRESS'.
Can you help me to learn more?
(Other definitions for progress that I've seen before include "Advancement" , "Move forward" , "Go forward" , "Course" , "Gradual improvement or development" .)